The invention relates to a synchronous programmable parallel-to-serial data converter having a programmable frequency ratio between a parallel input data and serial output data and to a programmable longitudinal time code generator utilizing the converter and which can be programmed for use in various magnetic recording systems and at selected tape speeds.
As well known in the art of magnetic recording and reproduction, a time code is generally recorded on the magnetic medium, for example tape, along with the information signal. The recorded time code is utilized to locate a portion of the recorded information if necessary for example for editing, video program production or other purposes. For example when providing broadcast quality video tape recording, generation and recording of a time code must conform to specific well defined standards. As it is well known these standards vary with different recording systems, such as NTSC, PAL, PAL-M, SECAM, etc.
It is well known to utilize for example a microprocessor to generate a time code in parallel form which then must be converted into serial data for recording on tape as a longitudinal time code. In video tape recording, such as utilizing a longitudinal, transverse or helical recording/reproducing format time code is known to be recorded as a longitudinal signal on an audio track by an audio transducer. As well known and in accordance with the above-indicated standards, the time code is measured as an arbritrary time of the day and it consists for all the above-indicated recording systems of 80 bits of which each group of 8-bits or a byte indicates among other values a particular value as follows: tens of hours; units of hours; tens of minutes; units of minutes; tens of seconds; units of seconds; tens of frames and units of frames, respectively. Consequently, when it is necessary to change the recording format or, alternatively, when it is desired to record the time code at slower or faster tape speed than normal playback speed, the parameters of the time code generation must be changed accordingly, to obtain synchronous recording thereof with the recorded information.
Prior art time code generators utilize relatively complex timing and pulse generating circuitry which cannot be readily modified to provide respective time codes adapted to the above-indicated changes of the recording parameters.